Power use of my Hotspot varieties –

It occurred to me after Bud tested his hotspots with the USB meter that I should look at my collection and find out how much power each was using. It is amazing what one can find out about these things. First up a small description of what I tested with the UM25C meter with a few variations where I could easily make changes. I still have a lot of options that I may test such as fans in and out of service but right now I did not have a convenient way to turn all the fans off or on as they are mounted inside the case etc.

Descriptions:

Hotspot DS2 is my home use duplex board with a 7 inch screen. This unit runs on a Pi 3B and I have put it in a case that has a cooling fan. The MMDVM board is the German (DF0EN, DB9MAT) board and it is mounted “OUTBOARD” of the pi case. I did this for two reasons, cooling and ease in changing the MMDVM boards on the Pi. I also have a BI7JTA duplex board and an N5BOC duplex board. (Still in flux on configurations.) Read more info about this setup here: ColoradoDigital.net

We all know that the Pi 3B+ run pretty hot, if you close it up in a case, and even though they are rated to …. A way hot number like 80 deg C before permanent damage occurs you might want to run much less. In some research I see that a “safe” number or recommended temp of 60 deg C = 140 degF is needed. I prefer to have my stuff run at a much lower temp so I can “touch” it and not get burned… I also note that watching the dashboard that it turns orange/yellow when it exceeds around 125 deg F=51 degC. So I must assume that the designers of the Pi intend for that to be the “warning” temperature so I do what I can to keep it below that limit.

Hotspot DS1 is a newer setup that for sure is in flux due to heat peaks, but worthy of testing. It is the new N5BOC board mounted in a Pi zero with a 3.2 inch Nextion screen. I had purchased a case online for the 3.2 screen that I must assume was designed for the pi zero (the holes in the back to mount were pi zero spots. It is much bigger than the usual Jumbo or Zum with the OLED screens but it was set up for the bigger 3.2 inch screen. It had no holes for ventilation and in the first day of use it ran up past 128F pretty quick. I since have added a couple of small slots in the bottom and some 3/32 holes in the top but even that is barely holding below 120degF so plans are in the future to add a small fan and maybe a switch for that fan?

Hotspot HS1 is one of my original units. It is a Pi zero with a Chinese Jumbo (simplex MMDVM) mounted on it and originally was in the basic black metal case but now resides in a C4labs case and mounts on my monitor, out of the way, It has an OLED screen on it.

Hotspot HS3 is again a Pi zero in the C4labs case but this unit has the newer simplex MMDVM from BI7JTA (zero offset?) and no OLED. I use this in my “GO” or “TRAVEL” box which houses this unit plus another similar unit HS4 and a large battery that can run for 1 to 2 days depending on what all is happening and I have 3.2 screens on each that sets in the top of the box or can be pulled up to see the activity.

HS 3 adn 4 are in that box below those screens. 

Hotspot HS4 is a Pi Zero with a generic Jumbo simplex MMDVM that does have a OLED on it and I use this for Dstar/Fusion in the “GO” box. It also has a 3.2 screen in the box that can come out for viewing, etc.

Testing:

I started by just putting my UM25C meter in the power line feeding each hotspot to find out the full power use for each, but then I figured I should find out how much (in amperage) some of the “add-on” components were using in case I had to run things on battery. Then to be fair on the duplex boards I put ran three tests on the DS2 hotspot with each of the three duplex boards I have, I hope but doing this all on the same Pi and 7 inch screen I could get a better idea of the three duplex boards in use. The results are below:

Hotspot DS2 – German board – in fan case with 7 inch: all estimated averages:

Startup current 0.14 amps

Initial reads? 0.23 to 0.30 amps

Screen start 0.68 amps

Operations starts and screen full = 1.20 amps drops to 0.950 amps with radio active

Idle current average = 0.87 amps (likely at no radio action)

Disconnect 7 inch screen 0.64 amps (whew that screen uses about 0.25 amps)

Over time the power fluctuated from 0.87 to 1.3 amps depending on modem useage , screen restarts or changes, etc.

Hotspot DS2 – BI7JTA board – in fan case with 7 inch:

Startup current 0.200 amps

Initial reads? 0.297 amps

Screen start 1.158 amps

Operations starts and screen full = 1.087 amps

Idle current average = 0.873 amps

Disconnect 7 inch screen 0.647 amps

Hotspot DS2 – N5BOC board – in fan case with 7 inch:

Startup current 0.230 amps

Initial reads? 0.325 amps

Screen start 1.170 amps

Operations starts and screen full = 1.095 amps

Idle current average = 0.870 amps

Disconnect 7 inch screen 0.636 amps

Hotspot DS1 – N5BOC board – on Pi Zero in the enclosed case no fan with 3.2 inch screen on USB to TTL connection. ( couldn’t put the other boards in this case due to size limits). Run temps here are about 115 deg F on idle but 129 deg F or more in active use.

Startup current 0.23 amps

Initial reads? 0.29 amps

Screen start 0.31 amps

Operations starts and screen full = 0.398 amps (single TS in operations)

Idle current average = 0.3265 amps (no radio action)

Disconnect 3.2 inch screen 0.255 amps

Hotspot HS1 – Chinese MMDVM on Pi Zero with OLED mounted in C4Labs case

Startup current 0.143 amps

Initial reads? 0.189 amps

Screen start 0.220 amps

Operations starts and screen full = 0.232 amps

Idle current average = 0.158 amps

Hotspot HS3 – new BI7JTA MMDVM (no OLED) using 3.2 Nextion and USB to TTL on a Pi Zero in C4labs case. Normal Idle run Temp is 108deg F

Startup current 0.205 amps

Initial reads? 0.262 amps

Screen start 0.314 amps

Operations starts and screen full = 0.287 amps

Idle current average = 0.206 amps

Disconnect 3.2 inch screen 0.149 amps

Hotspot HS4 – Chinese MMDVM on Pi Zero with OLED but using 3.2 Nextion and USB to TTL in C4Labs case. Normal run temp is same or similar to the HS3 but in strong use these two go up to 125 deg F.

Startup current 0.135 amps

Initial reads? 0.223 amps

Screen start 0.270 amps OLED = 0.213 amps?

Operations starts and screen full = 0.323 amps

Idle current average = 0.208 amps OLED = 0.154 amps?

Disconnect 3.2 inch screen 0.154 amps

Openspot – An original Openspot just for comparisons.

Startup current 0.110 amps

Initial reads? 0.129 amps

Screen start none

Operations starts and radio talk = 0.202 amps

Idle current average = 0.177 amps

Conclusions

Amazing that the smaller screen and the N5BOC board used so much less power on Pi Zero than DS2-Pi3B+ and big screen. I will need to rerun some tests when I get the A+ boards/cases and swap out some of the B+ boards. Will also need to do some tests for the go box on the jumbo boards and A+ Pi.

The B+ board sure dictated the power useage. All three modems were very similar in usage at screen starts, operations both with radio on and off. On all of them it appears the hotspots use 0.87 +/- amps and when the radio is on it jumps to about 1.1 amps for all of them. I was surprised that the German (revision 1.3 – 6/2018) board did not run a bit more efficient than the BI7JTA (version 1) as it is surely a year newer but there is not that much difference and beyond that the N5BOC made for the Pi zero in a very small space and , I thought, advertised to be much more efficient did not prove to be any different power wise on the B+ board..

The big screen uses about twice as much amperage to run as the 3.2 screen. Logical as it is more than twice the size. From the results it appears the 3.2 screen used about 0.1 amp +/- and the 7 inch used 0.24 amps +/_

It is nice to see that the Jumbo’s with the simple OLED are reasonably power efficient as compared to the old OPENSPOT. Not a lot of difference and it has a screen. The Led’s on the Jumbo are really bright but you can’t read the lettering to know which is which so it is necessary to “memorize” position versus LED to know what is going on but not a horrible problem. For me the OLED is a step better than no screen but way small for old tired eyes.

I really like my 7 inch screen, I can see it just about anywhere in the shack but it is a power HOG!… at least on the 3B+ once I get it on an A+ and test, will see if it comes down reasonably, AS per Buds early report on the various Pi’s…

The only useful info from all this testing is backing out how long your “big” battery should last if you have a mobile hotspot in one of these configurations. My 10,000 mAH battery does pretty well with the hotspots on the 3.2 screens and can last a bit over 24 hours running both. Unless there is a lot of traffic and then it will go down. I am sure there are numerous variable to test for power conservation but this is a starting point.

WD0AJG